It is known that bone marrow stromal cells form bone marrow micro environment of immunologic, hematopoietic system etc, and they produce and secret essential factors to induce of proliferation and differentiation of stem cells, e.g. IL-7, SCF, IL-11, M-CSF, G-CSF, GM-CSF, IL-6, TGF-β, LIF etc. It is also made clear that a certain bone marrow stromal cells are related to bone metabolism (Kenneth Dorshkind Annu. Rev. Immunol. 8, 111-137. 1990). However, roles of stromal cell are not reconstituted completely from only isolated factors yet. It may suggest that existence of any factors which are not isolated yet.